This invention relates to an air bag assembly, and more particularly to an air bag assembly including an inflatable air bag cushion and one or more tethering elements of variable operative length in attached relation to surfaces of the air bag cushion wherein the inflated profile of the air bag cushion is controllable by varying the operative length of the tethering elements during use of the air bag cushion. The profile of the air bag cushion may be adjusted based upon the measured size and/or position of the vehicle occupant to be protected.
It is well known to provide an air bag assembly including an inflatable air bag cushion for protecting the occupant of a transportation vehicle. In an automotive vehicle such air bag assemblies are typically located within the hub of the steering wheel and in a recess in the vehicle instrument panel for protection of the vehicle occupants seated in opposing relation to such assemblies. Additional air bag assemblies may be located within the seats and/or door panels for protection of the occupants during a side-impact event. It is also known to utilize inflatable curtain-like structures for deployment from the structural pillars or roof line of the motor vehicle so as to promote restraint and protection of the vehicle occupant during a roll-over event.
Air bag assemblies typically include an inflatable cushion in fluid communication with a gas emitting inflator. Upon sensing certain predetermined vehicle conditions, such as a certain level of vehicle deceleration, the inflator discharges a fixed amount of inflator gas thereby forcing the air bag into a deployed position. The inflator gas occupies the available volume within the air bag cushion thereby forcing the air bag cushion to expand outwardly to the extent permitted by its construction. The pressure within the air bag cushion upon deployment is proportional to the quantity of inflator gas expelled into the air bag and inversely proportional to the volume occupied by the inflator gas within the air bag. As the occupant comes into contact with the expanded air bag, the inflator gas is forced out of the air bag thereby dissipating the kinetic energy of the occupant.
Absent restraint, an inflated body tends to assume a generally spherical profile. In order to provide control over the inflated shape of the air bag cushion, it is known to utilize tethering elements in the form of straps or webs extending between surfaces of the air bag cushion to thereby hold the surfaces in fixed orientation relative to one another upon inflation. The selection and length of such tethering elements can thus be used to establish a desired inflated profile. However, once the tethering elements are attached to the surface, the inflated geometry of the cushion is fixed and is not subject to adjustment.
As will be appreciated, the preferred inflated profile of the air bag cushion may vary depending upon the severity of the activating impact event and/or upon the size of the occupant to be protected and/or upon the position of the occupant to be protected. Thus, the ability to effectively control the inflation characteristics of the air bag cushion is potentially desirable. In order to provide a degree of control over the inflated profile of the air bag cushion it is known to use an inflator that has varied levels or stages of inflator gas output in response to the sensing of different vehicle or occupant conditions. Thus, it is generally known in the prior art to utilize so-called xe2x80x9cdual-stagexe2x80x9d inflators that discharge predetermined amounts of gas at one or two levels. However, these dual-stage inflators are more complex than typical inflators and have the limitation of typically providing only discrete levels of gas output. Moreover, the use of such dual-stage inflators provides control over only the amount of inflator gas which is discharged and does not provide control over the expanded geometry of the inflated air bag cushion. That is, so long as the air bag has a fixed volumetric capacity, the inflator gas will tend to fill that capacity and the expanded configuration of the air bag will be generally the same although the pressure will vary.
In order to provide an additional degree of freedom in the control of air bag performance, it has been suggested to utilize air bag cushions which incorporate sewn or woven in seams within the air bag to control the expanded geometry of the inflated air bag wherein the seams separate upon the introduction of pressures exceeding a certain level thereby freeing the air bag cushion from the restraint imposed by the seams at lower pressures. In order for such break-away seams to provide controlled expansion, the application of such seams must be performed with substantial precision such that seam separation will occur in a highly reproducible and predictable manner. As will be appreciated, due to the large number of variables involved in the introduction and separation of such break-away seams, such requisite precision and reproducibility may be difficult to achieve. Moreover, even when such breakaway seams are utilized, the expansion which occurs may be in all directions. In some applications it is believed that preferential expansion in the depth of the air bag (i.e. towards the occupant to be protected) may be desirable.
The present invention provides advantages and alternatives over the prior art by providing an air bag assembly including an inflatable air bag cushion operatively attached to one or more profile restricting tether elements having an operative length which may be selectively adjusted to provide desired inflation and impact response characteristics.
According to one aspect of the present invention, an air bag assembly is provided having an inflatable cushion selectively deployable to a controlled geometry desired in view of the position and/or size of the occupant to be protected such that an air bag of substantial depth and increased volume is available to protect occupants such as larger stature persons who are seated further away from the location of cushion deployment, while a smaller air bag volume of diminished depth is available to protect occupants such as smaller stature persons seated closer to the location of cushion deployment. A highly efficient mechanical release system may be used to adjust the operative length of internal tethers within the cushion thereby permitting enhanced controlled expansion of the cushion. Preferably the tethers maintain a degree of restraint across the surface of the cushion following adjustment.
According to another aspect of the present invention, an air bag assembly is provided having an inflatable cushion including a plurality of tethering elements extending between points of fixed connection at the surface of the cushion. At least a portion of the tethering elements are additionally attached along their length to the surface of the cushion at points of sliding connection between the points of fixed connection such that dynamic tensioning is maintained within the tethering elements over a range of inflation conditions.
The air bag assembly according to the present invention offers substantial versatility in the protection of large numbers of diverse occupants. Moreover, the air bag assembly of the present invention provides a simple, cost effective and highly reproducible mechanism for controlling the profile and performance of deployed air bag cushions even when using a traditional single stage inflator.